LASER-INDUCED THERMOTHERAPY (LITT) - IN-V ITRO AND IN-VIVO INVESTIGATIONS OF CANINE MAMMARY-TUMORS

In vitro and in vivo laser induced interstitial thermotherapy (LITT) w as carried out as a minimal invasive alternative to the conventional s urgical treatment of canine mamma tumors. A special laser applicator w ith a circumferential radiation feature was positioned percutaneously in the center of the tumor using a puncture system. The applicator was connected to a Nd:YAG laser (1064 nm). The morphological changes due to different laser parameters (power density 5 and 7 Watt; radiation t ime 300, 450, 600, 750 and 900 sec) were investigated in in vitro expe riments using native mammary tumors. The results showed that the size of the coagulation area which varied between 1.42 x 0.96 cm and 2.96 x 1.96 cm was dependent on the power density and irradiation time. The histology of the samples revealed morphological changes in the treated area which was defined as cytolysis. The seven female patients treate d (mean age was 12.4 years) had all been classified as high risk patie nts in which conventional surgical therapy was not recommended. A lase r power density of 5 Watts was applied at every puncture point for 450 sec or 600 sec according to the size of the tumor to be treated. Imme diately after treatment a large edema developed and an erythema appear ed on the skin surface overlying the tumor whereas the neighbouring no rmal tissue showed no reaction to the treatment. Each animal was exami ned 7, 14 and 60 days postoperatively. A mean reduction of the tumor v olume of 58 % was recorded. Complications were minimal.